Permeable-base transistors have been suggested previously. In particular, devices have been suggested wherein the collector or anode and the emitter or cathode regions are formed exclusively from a semiconductor such as silicon, as suggested by Rothman, et al. in IEDM Technical Digest 1982 (IEEE, New York, 1982) pages 650-653 and Nishizawa, et al., IEEE Trans. Electron Devices ED-22, 185 (1975), or gallium arsenide, as discussed by Bozler, et al., IEEE Trans. Electron Devices ED-27, 1128 (1980). Rothman, et al., supra, and Bozler, et al., supra, suggest that the base region be formed from a metal. Nishizawa, et al., supra, suggest a base region formed from degenerate-semiconductor fingers.
In these devices, unipolar current flow from the emitter to the collector is controlled by carrier motion through the semiconducting regions that separate the base regions. These base regions act like a gate by either allowing carriers to pass through or not, depending upon the potential barriers created by the specific voltage bias conditions. Since these devices are limited by bulk current flow through the semiconducting regions, fast switching speeds are attainable, particularly for those structures fabricated with gallium arsenide which has a higher mobility than silicon. However, since the grid spacing must be comparable to the depletion width, submicron technologies are needed in the design of the devices.